Enzymes having proteolytic activity at alkaline pH are known and have been described in several references, such as U.S. Pat. Nos. 3,674,643 and 4,002,572. Proteolytic enzymes produced by cultivation of members of the genus Bacillus constitute the major source of proteolytic enzymes used in detergent washing compositions. Classified generically as serine proteases, these proteolytic enzymes generally are characterized by sensitivity to diisopropylphosphofluoridate and phenylmethylsulfonyl fluoride (PMSF), resistance to thiol reagents and metal chelators, molecular weights ranging from about 20,000 to about 28,000 daltons, and isoelectric points in the alkaline range. As detergent additives, it is also important for the proper functioning of these enzymes that they be active in solutions at alkaline pH values and in the presence of sequestering agents, surfactants, and in some cases, oxidizing agents.
A basic trend in the detergent market has been for manufacturers to formulate detergents with builder systems other than sodium tripolyphosphate and to provide consumers with products that function at lower wash temperatures. Accordingly, the industry has supplemented their products with enzymes (e.g., proteases and/or amylases) to compensate for detergency reductions. In general, however, proteases formulated into detergents such as Esperase.RTM. and Alkalase.RTM. from Novo Industries (Bagsuaerd, Denmark), Maxatase.RTM. and Maxacal.RTM. from Gist-Brocades (Delft, Holland) and Milezyme.RTM. from Miles Laboratories (Elkhark, IN) have temperature optima at about 60.degree. C. The enzyme of this invention has a temperature optimum between 45.degree.-50.degree. C. and therefore is more suited for warm (30.degree.-40.degree. C.) or cold (15.degree.-30.degree. C.) temperature washings. Furthermore, as shown below, the protease of this invention exhibits a significantly higher specific activity at 40.degree. C. using casein as substrate as compared to several enzymes on the market.
Accordingly, it is an object of the invention to provide an enzyme which is highly active on proteinaceous material at high pH and moderate temperatures. It is also an object of the present invention to provide a novel proteolytic enzyme which exhibits good stability under alkaline conditions.
It is an additional object of this invention to provide a process for preparation of such an alkaline proteolytic enzyme.
Other objects and advantages of the invention will become apparent from the following detailed description.